Core material in telecoil for an audio induction loop ?

[Externet]

Hi.
Planning to build a telecoil to drive an amplifier for earphone, voice range only... Should I use plain iron or ferrite ? Would a plain nail perform ? Is there a convenient geometry of the core/coil for better sensitivity ?
Would a high turn count reed relay bobbin be satisfactory over the core ? I have a couple waiting to be used in something... Low turn count ferrite coils are abundant canibalized from defunct SMPSs.

----> https://www.tecear.com/images/T-coil.jpg

 

[dr pepper]

The amount of copper you'd need to get a ferrite core to work at audio would be great, commercial smps's use stuff like 3c85 which isnt good at low audio freq's.
Silicon steel as per mais power trannys is much better.
However the size of the coil affects range with hearing aids, an air coil the size of a window frame would give you a good range if you've space.
Check the spec of the amp driving the coil, there will be a minimum inductamce spec that you'll have to design to.

 

[Externet]

Thanks, doctor.
Yes, agree, forget the ferrite. Will try iron as steel may get magnetized. Do not know if getting magnetized would affect anything anyway. Hey! there is steel nails for concrete too, so I can try both. Silicon steel in tiny rods - do not know where to find them.
The 'amplifier driving the loop' and the loop is not discussed... that is air core. Just the receiving T-coil.

 

[chemelec]

Silicon Steel is best.
Soft Iron is Second Best.
(A Bundle of 10 or so, Straight Steel Wires is good.)
I have a roll of 14 AWG, Black Colored Iron Wire that I use for some types of transformers and pickups.
(Bought at a Hardware Store.)

 

[Tony Stewart]

loop gap must be less than diameter.

 

[dr pepper]

Rob the laminations from a dead power transformer, they are usually silicon steel.
Magnetization can cause problems, Remanence is an issue in power transformers, and for this application saturation on one half of the waveform would be an issue.